There definitely needs to be an update that improves the acceleration of the BR 642 (Siemens Desiro) diesel multiple unit. This is so bad that timetables can never be adhered to. Up to 40 km/h the train accelerates very well, but above 40 km/h it gets worse and worse, usually only 1 km/h in 30 seconds. This never corresponds to reality!
I don't think this belongs to the suggestions. This page is more for ideas for new trains, routes and play functions. You can better place this problem in the player feedback at the Maintalbahn page.